The present invention relates to implantable prosthetic heart valves with flexible leaflets. More particularly, it relates to a prosthetic heart valve system including a device for effectuating prosthetic heart valve stent post deflection during implantation thereof.
Various types and configurations of prosthetic heart valves, used to replace diseased natural human heart valves, are known in the art. The actual shape and configuration of any particular prosthetic heart valve is, of course, dependent to some extent upon the valve being replaced (i.e., mitral valve, tricuspid valve, aortic valve, and pulmonary valve). In general terms, however, the prosthetic heart valve design attempts to replicate the function of the valve being replaced and thus will include valve leaflet-like structures. With this in mind, prosthetic heart valves are generally classified as either forming relatively rigid leaflets and those forming relative flexible leaflets.
As used throughout this specification a “prosthetic heart valves having relatively flexible leaflets” (or “prosthetic heart valve”) encompass bioprosthetic heart valves having leaflets made of a biological material as well as synthetic heart valves having leaflets made of a synthetic (e.g., polymeric) material. Regardless, prosthetic heart valves are generally categorized as having a frame or stent, and those which have no stent. The stent in a stented prosthetic heart valve normally includes a substantially circular base (or stent ring), around which an annular suture material is disposed for suturing the prosthesis to heart tissue. Further, stent forms at least two, typically three, support structures extending from the stent ring. The support structures are commonly referred to as stent posts or commissure posts and include an internal, rigid yet flexible structure extending from the stent ring, covered by a cloth-like material similar to that of the annular suture material. The stent or commissure posts define the juncture between adjacent tissue or synthetic leaflets otherwise secured thereto. Examples of bioprosthetic heart valves are described in U.S. Pat. No. 4,106,129 to Carpentier et al., and U.S. Pat. No. 5,037,434 to Lane, the teachings of which are incorporated herein by reference. These disclosures detail a conventional configuration of three leaflets wherein one leaflet is disposed between each pair of stent or commissure posts.
Implantation of a prosthetic heart valve presents numerous technical challenges, regardless of the prosthesis' configuration. With respect to stented prosthetic heart valves, inventive efforts have focused on minimizing the complications associated with mitral valve replacement. In this regard, a prosthetic mitral valve is normally implanted by placing the prosthesis into the mitral valve annulus with the stent posts projecting blindly deep into the patient's left ventricle. Due to a lack of visibility through the prosthetic valve, a surgeon can inadvertently loop sutures around the stent posts during suturing of the annular suture ring portion of the prosthesis. Similarly, the extending stent posts may undesirably “snag” on chordae or trabeculae inside the left ventricular cavity. To avoid these complications, various prosthetic valve holders have been designed that inwardly retract or deflect and hold the mitral prosthetic stent posts during implantation. In general terms, available prosthetic mitral heart valve holders include an elongated handle and a holder mechanism. The holder mechanism is secured to the stent ring and adapted to inwardly deflect the stent posts upon rotation of the handle. In this regard, the handle extends proximally from the holder mechanism, opposite the stent posts. An exemplary prosthetic mitral heart valve holder is described in U.S. Pat. No. 4,865,600 to Carpentier et al.
Medtronic Hancock® mitral valves are available mounted to a holder providing a mechanism for inward deflection, as illustrated in the brochures: “A New Dimension—The Hancock II Bioprosthesis,” Medtronic Inc., 1991, publication number UC8903226EN and “A New Light on the Hancock Bioprosthesis,” Medtronic Inc., 1988, publication number UC8801713EN, both incorporated herein by reference in their entireties. This holder includes a ratcheting spool, mounted below the sewing ring, which when rotated by means of an attached handle, pulls lengths of suture inward, in turn pulling sutures extending upward though the commissure posts and between the commissure posts downward, to deflect the commissure posts inward.
The above-described prosthetic mitral heart valve holder devices are well-suited for mitral valve replacement. In general terms, the mitral valve surgical site is relatively easily accessed, with minimal anatomical obstructions “above” or away from the implant site. Thus, the surgeon is afforded a large, unobstructed area for locating and maneuvering the handle as well as performing necessary procedural steps (e.g., suturing the annulus suture ring to the heart tissue) with minimal or no interference from the handle and/or mechanism. This mitral valve implant site characteristic allows the currently available prosthetic mitral valve holder to assume a relatively bulky and complex form.
Aortic prosthetic heart valve implantation presents certain constraints distinct from those associated with mitral valve replacement. In particular, with aortic heart valve implantation, a surgeon is often faced with little room to maneuver. Depending upon the type of aortotomy performed, the surgeon may first have to pass the prosthesis through a restriction in the aorta known as the sinotubular junction, which is often times smaller than the tissue annulus onto which the prosthetic heart valve will be sutured. The surgeon must then “seat” the prosthetic heart valve securely in or on the tissue annulus with downward pressure. The surgeon must then tie down all annular sutures (via knots), ensuring that a hemostatic seal is made. Finally, the surgeon must cut-off all sutures in close proximity to the knots. Relative to the orientation of the aortic prosthetic heart valve during the implant procedure, the stent posts extend proximally toward the surgeon (as opposed to the distal stent post direction associated with mitral valve replacement). Thus, while the concern for “snagging” of the stent posts (i.e., inadvertently looping sutures about stent post(s)) is minimal during aortic prosthetic heart valve implantation, the proximally extending stent posts associated with the stented prosthesis interfere with the various other maneuvers required of the surgeon.
In light of the above, it would be desirable to inwardly deflect the stent posts during implantation of the aortic prosthetic heart valve. Unfortunately, the above-described mitral prosthetic heart valve holders are of little value for aortic valve replacement procedures in that the holder positions the handle to extend in a direction opposite that of the stent posts. As such, the handle would have to be removed in order to implant the aortic prosthetic heart valve. Without this handle component, the holder cannot be operated to inwardly deflect the stent posts. Attempts have been made to correct this incompatibility by reconfiguring the holder to extend the handle in the same direction as the stent posts, as described, for example, in U.S. Pat. Nos. 5,476,510 and 5,716,410, both to Eberhardt et al., the teachings of which are incorporated herein by reference.
More recently, a few surgeons have begun to employ a self-fashioned technique to approximate (i.e., inwardly deflect) stent posts of an aortic prosthetic heart valve. The technique entails threading a suture through the cover material otherwise covering the stent posts. A surgical tube is slidably placed over the suture and is then forced toward the prosthetic heart valve, causing the stent posts to inwardly deflect. A surgical clamp is then used to temporarily lock the tube along the suture, theoretically maintaining the stent posts in an approximate position. Unfortunately, it is impossible for the surgeon to know or otherwise confirm the degree to which the stent posts have deflected. To this end, the prosthetic heart valve can be damaged if the stent posts are overly deflected and/or maintained in an overtly deflected position for an extended period. The valve can also be damaged by the surgeon if cutting sutures are used or the suture needle employed to thread the suture through the stent posts is inappropriately passed through critical stress areas of the valve, leading to premature valve failure. Further, the above technique continues to require an elongated component (surgical clamp) that impedes convenient handling/implant of the prosthetic heart valve. Thus, this makeshift approach is not optimal.
Devices for assisting in the implantation of stented prosthetic heart valves are essentially limited to mitral valve replacement procedures. These stent posts deflection apparatuses are relatively bulky and mechanically complex. Conversely, rudimentary techniques improvised by some surgeons are unreliable and may lead to prosthesis damage. Therefore, a need exists for a preassembled stent post deflection device that is safe, simple in form and operation, and appropriate for any heart valve location, including the aortic heart valve.